Quasi-Cubic Magnetite/Silica Core-Shell Nanoparticles as Enhanced MRI Contrast Agents for Cancer Imaging (original) (raw)
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Contrast media & molecular imaging
Monodisperse mesoporous silica (mSiO 2 ) coated superparamagnetic iron oxide (Fe 3 O 4 @mSiO 2 ) nanoparticles (NPs) have been developed as a potential magnetic resonance imaging (MRI) T 2 contrast agent. To evaluate the effect of surface coating on MRI contrast efficiency, we examined the proton relaxivities of Fe 3 O 4 @mSiO 2 NPs with different coating thicknesses. It was found that the mSiO 2 coating has a significant impact on the efficiency of Fe 3 O 4 NPs for MRI contrast enhancement. The efficiency increases with the thickness of mSiO 2 coating and is much higher than that of the commercial contrast agents. Nuclear magnetic resonance (NMR) relaxometry of Fe 3 O 4 @mSiO 2 further revealed that mSiO 2 coating is partially permeable to water molecules and therefore induces the decrease of longitudinal relaxivity, r 1 . Biocompatibility evaluation of various sized (ca. 35-95 nm) Fe 3 O 4 @mSiO 2 NPs was tested on OC-k3 cells and the result showed that these particles have no negative impact on cell viability. The enhanced MRI efficiency of Fe 3 O 4 @mSiO 2 highlights these core-shell particles as highly efficient T 2 contrast agents with high biocompatibility.
Chemistry-an Asian Journal, 2009
Oleic acid stabilized superparamagnetic iron oxide nanoparticles (SPION) were selected as the cores for fabrication of sub-50-nm monodisperse single-loaded SPION@SiO2 core–shell nanostructures. Parameters that influence the formation of SPION@SiO2 in the water-in-oil reverse microemulsion system have been systematically investigated. The sufficiently high concentration of well-dispersed SPION, together with an appropriately low injection rate of tetraethoxysilane, were found to be the keys to efficiently prevent the homogeneous nucleation of silica and obtain a high-quality single-loaded core–shell nanocomposite. A more detailed mechanism for incorporating oleic acid capped inorganic functional nanoparticles into silica is proposed on the basis of previous reports and our new experimental results. Finally, the as-synthesized SPION@SiO2 nanospheres are exploited as an MRI-enhanced contrast agent, and their contrast effect in solution is tested by using a clinical MRI instrument.
The current nanotechnology era is marked by the emergence of various magnetic inorganic nanometer-sized colloidal particles. These have been extensively applied and hold an immense potential in biomedical applications including, for example, cancer therapy, drug nanocarriers (NCs), or in targeted delivery systems and diagnosis involving two guided-nanoparticles (NPs) as nanoprobes and contrast agents. Considerable efforts have been devoted to designing iron oxide NPs (IONPs) due to their superparamagnetic (SPM) behavior (SPM IONPs or SPIONs) and their large surface-to-volume area allowing more biocompatibility, stealth, and easy bonding to natural biomolecules thanks to grafted ligands, selective-site moieties, and/or organic and inorganic corona shells. Such nanomagnets with adjustable architecture have been the topic of significant progresses since modular designs enable SPIONs to carry out several functions simultaneously such as local drug delivery with real-time monitoring and imaging of the targeted area. Syntheses of SPIONs and adjustments of their physical and chemical properties have been achieved and paved novel routes for a safe use of those tailored magnetic ferrous nanomaterials. Herein we will emphasis a basic notion about NPs magnetism in order to have a better understanding of SPION assets for biomedical applications, then we mainly focus on magnetite iron oxide owing to its outstanding magnetic properties. The general methods of preparation and typical characteristics of magnetite are reviewed, as well as the major biomedical applications of magnetite.
Journal of the American Chemical Society, 2011
Magnetic resonance imaging (MRI) is one of the most powerful medical diagnosis tools because MRI can provide images with excellent anatomical details based on the soft tissue contrast and functional information in noninvasive and real-time monitoring manner. 1,2 The sensitivity of MRI can be greatly improved by the contrast agents that enhance the contrast of the region of interest from background. The MRI contrast agents are generally categorized according to their effects on longitudinal (T 1 ) and transversal (T 2 ) relaxations, and their ability is referred to as relaxivity (r 1 , r 2 ). The area wherein fast T 1 relaxation takes place appears bright, whereas T 2 relaxation results in the dark contrast in the MR images.
Towards MRI T2 contrast agents of increased efficiency
Journal of Magnetism and Magnetic Materials, 2015
Magnetic nanoparticles can be efficient contrast agents for T2 weighted magnetic resonance imaging (MRI) after tuning of some key parameters such as size, surface state, colloidal stability and magnetization, thus motivating the development of new synthetic pathways. In this paper we report the effects of surface coating on the efficiency of two different types of iron based nanoparticles (NPs) as MRI contrast agents. Starting from well-defined hydrophobic iron oxide nanospheres and iron nanocubes of 13 nm size, we have used three methods to increase their hydrophilicity and transfer them into water: surface ligand modification, ligand exchange or encapsulation. The NPs obtained have been characterized by dynamic light scattering and transmission electron microscopy, and the relaxivities of their stable colloidal solutions in water have been determined. Among all samples prepared, iron nanocubes coated by silica display the highest relaxivity (r 2) value: 628 s À 1 mM À 1 .
Journal of the Korean Physical Society, 2010
We synthesized iron-oxide (Fe3O4) nanoparticles by using the reverse micelle method and coated them with biocompatible silica. The coated nanoparticles were found to be spherical in the TEM images and showed a uniform size distribution with an average diameter of 10 nm. The T1 and the T2 relaxation times of hydrogen protons in aqueous solutions with various concentrations of silicacoated nanoparticles were determined by using a magnetic resonance (MR) scanner. We found that the T2 relaxivity was much larger than the T1 relaxivity for the nanoparticle contrast agent, which reflected the fact that the T2 relaxation was mainly influenced by outer sphere processes. The T2 relaxivity was found to be 15 times larger than that for the commercial Gd-DTPA-BMA contrast agent. This result demonstrates that silica-coated iron oxide nanoparticles are applicable as a T2 agent in magnetic resonance imaging.
In vivo evaluation of magnetite nanoparticles for use as a tumor contrast agent in MRI
Magnetic Resonance Imaging, 1996
Magnetite nanoparticles, coated by three different artificial polypeptides, were conjugated to an antibody specific to the carcinoembryonic antigen (CEA). To protect the particles from fast blood elimination, the coats were modified by various sugars, polyethyleneglycol, albumin, and sialoproteins, respectively. The protective effect was determined by using a specific in vitro test and by analyzing the biodistrlbution of the nanoparticles in nude mice grafted with CEA-tumors. In particular, a prolongation of the blood circulation time has been expected, if a natural modifier is attached to the coated nanoparticles. Although the elimination rate could hardly be decreased by any modifiers, the tumor accumulation is slightly improved by using the specific sialoprotein glycophorin B. The usefulness of nanoparticles as image contrast agents is probably limited by their microdistribution within the tumor tissue. The requirements for a contrast agent to be highly tissue specific are discussed.
Magnetic resonance imaging (MRI) is one of the most powerful medical diagnosis tools because MRI can provide images with excellent anatomical details based on the soft tissue contrast and functional information in noninvasive and real-time monitoring manner. 1,2 The sensitivity of MRI can be greatly improved by the contrast agents that enhance the contrast of the region of interest from background. The MRI contrast agents are generally categorized according to their effects on longitudinal (T 1 ) and transversal (T 2 ) relaxations, and their ability is referred to as relaxivity (r 1 , r 2 ). The area wherein fast T 1 relaxation takes place appears bright, whereas T 2 relaxation results in the dark contrast in the MR images.